This invention relates to filters generally and more particularly to diesel engine fuel filters of the replaceable cartridge variety.
The cartridge type of replaceable filter element has found wide spread application in providing a particular convenience for interchange of the filter medium. In many instances, the spin on type of filter cartridge is utilized as this provides the additional convenience of simply threading and unthreading the cartridge to accommodate the interchange.
Previous top loading cartridge filter designs have divided the filter housing and the filter element into separable entities usually comprising three parts, namely the disposable filter element, the filter housing and the filter cover assembly. These separate components have enabled manufacturers to offer sturdy, permanent filter housings while minimizing replacement element components and costs.
Spin on filter elements were later developed which were comprised of an inseparable filter housing and element assembly (usually disposable) along with a non-disposable head or cover assembly. Spin on elements initially offered convenience in element change over cartridge elements, but passed increased replacement element costs onto the end user. They were also less convenient than normal in top loading configurations.
Changing the filter element on the typical top loading cartridge filter involves draining the housing below the filter cartridge. The cover assembly and cartridge element are then removed from the housing in two separate operations. This can be time consuming and inconvenient in that the filter element has usually been submersed in the fluid and cannot be extracted by hand without contacting the fluid.
In changing a typical top loading, spin on unit, the element/housing must be completely drained of fluid before unscrewing from the head assembly to avoid spillage. This often involves a significant waiting period for the housing to drain completely. Spin on element replacement is more expensive than similar cartridge element replacement because the element and housing are inseparable and both must be disposed of.
The spin on concept especially in top loading applications, did not vastly improve element change out convenience over cartridge elements, but it did increase replacement elements costs. As a result, there has been a need for a top loading element design which would conveniently spin on and off, while avoiding the multiple operations and mess associated with cartridge element change out. It would also be necessary in such design to avoid the higher cost associated with the spin on type of element replacement.